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New submitter Ben_R_R writes "The Japan Aerospace Exploration Agency has created a camera that can 'see' radioactive contamination by detecting gamma rays emitted by radioactive cesium and other substances. The camera has been tested in the disaster evacuation zone around Fukushima. The image captures levels of radiation in six different colors and overlays the result over an image captured with a wide angle lens."

Detecting gamma rays is pretty easy. Detecting within a few degrees which direction they came from is much harder. Lenses and mirrors won't work (at least, at any reasonable scale) to form an image. You could have two layers of detector, and measure the location of the gamma ray as it passes through both. You could look for Compton scattered electrons from the gamma ray, which would be easier to determine the direction of, but I don't think that would fit in something camera sized.

I'm also curious to know what exposure time the gamma ray camera needs - I'm guessing it will be pretty long - minutes, at least, maybe hours.

I saw the camera on NHK World and it is not what you may think is camera sized. It is a big cube with about 1 m sides. It also includes a small optical camera, so that you get a composite of the visual picture and the gamma radiation distribution. It is supposed to be used to check the buildings in contaminated areas and see where the radioaktive material is located.

On any given interaction, you might have a problem. But, what if you averaged over a large period of time? Sure, the resulting image may be blurry, but a blurry photo is better than no photo. It's not as if you're trying to read text written in radioactive cesium ink. You just want to know "That corner's hot, this corner's not."

You could have two layers of detector, and measure the location of the gamma ray as it passes through both.

Photons don't work like this; if you measure its position at one point then its momentum is undefined. (In classical terms, one would say that the photon interacts with the first detector, e.g. gets diffracted)

Detecting gamma rays is pretty easy. Detecting within a few degrees which direction they came from is much harder. Lenses and mirrors won't work (at least, at any reasonable scale) to form an image.

Well, the obvious solution to how it works is light-field imaging. To which you may have heard of the Lytro camera that allows one to take pictures and refocus them later. A light-field camera takes not only the intensity of the light hitting it, but also direction (allowing for refocusing).

This gamma ray camera from the same institute [kyoto-u.ac.jp] may be something related? It seems to use Scintilation from a dislocated electron (which gives away path and energy) combined with the point of impact of the gamma ray on a detector plate.

There are two main imaging techniques that work in moderate-energy gamma-rays: Coded Aperture [nasa.gov] which use a shadow mask; and Compton Imaging [stanford.edu].

According to this article [enformable.com] the camera uses Compton Imaging. In this technique you look at gamma rays that scatter off of one detector and into another. Each detector tells you where the interaction occurred and how much energy was deposited. From this information, you can derive for each gamma ray that it came from somewhere on a hollow cone (with its tip at the first

When I readed the topic, I just tought "Oh, someone invented Camera what can see light, AMAZING!"Of course I know it was only about ionizing radiation and not just anykind radiation like visible light.

I'm pretty sure that I remember radiation from nuclear decay being discovered because it fogged photographic film, so the idea of a camera that detects it is not exactly novel. Presumably the real news is the sensitivity - being able to detect a lump of uranium by putting a photographic plate next to it for 12 hours is not nearly as useful as having it show up when you take a quick picture.

Detecting the radiation is trivial. Even any old digital camera sensor can do that. The trick is detecting where it came from. A regular camera uses a lens to accomplish this. However, lenses don't work on gamma rays.

Usually, you just put a scintillating crystal, e.g. thallium-doped sodium iodide, in front of your detector. Gamma photon hits crystal, crystal emits photon in the visual range, photomultiplier detects visual photon. TFA is somewhat silent on how this differs from your run of the mill gamma camera which has been known for half a century by now.

The big difference is that a scintillator or geiger tube is equivalent to a simple eye that just detects light levels. That can't be used to create a usable image. I suspect they have something like an insectoid compound eye going on.

The big difference is that a scintillator or geiger tube is equivalent to a simple eye that just detects light levels. That can't be used to create a usable image. I suspect they have something like an insectoid compound eye going on.

Or just put a lead collimator in front of a scintillator film on top of a CCD. Bingo, instant gamma camera. I've been doing this for years for SPECT imaging.

Detecting gamma rays on a flat sensor is one thing. But how do you actually image gamma rays? You cannot use a lens or curved mirror. A cursory check on google/Wikipedia does not answer this. I can only think of a pinhole camera, which is very inefficient and would have to deal with radiation passing through the supposedly opaque walls.

Scintigraphy is not only used for mere detection, but is in routine clinical use for imaging. You can go the pinhole route, but usually go with a movable collimator and movable detector, scanning the image. Now, if those guys have something that can snap a picture just like an optical camera, that would be interesting - but TFA is unfortunately silent on the details.

My brother helped develop a pinhole scintillation camera in conjunction with Bendix in Ann Arbor in 1971. First application was thyroid imaging. Exposure times were rather long. They were also working on tomography software... on a PDP-11.

Property of these crystal detectors is that they give you zero directional information, essential in a device named 'camera' I'd say. The geometry of the casing helps you slightly, but I suppose the JAXA folks figured out an altogether new way of imaging.

Yeah, the detector is non-directional. That's why you use a collimator and scan the object by moving the collimator and the camera. Leads to long exposure times and an unwieldy mechanical setup - I'd be interested if they solved it differently, too. They did leave out the interesting parts in TFA, though.

Oh great, now we're going to be overwhelmed with Japanese tourists taking pictures of radioactive things!

Great scene; but it's really funny how the "Japanese tourist" meme has so much died out. We're all Japanese tourists now, with the average teenage girl much more intrusive than they ever were (I never remember a Japanse tourist who wasn't really careful not to get in the way with his camera...the main problem was always the way the waited politely for everybody to be gone making you feel a bit rude for walking through the scene.. ). It's really amazing how they were so much fore runners of modern "western

The article doesn't discuss how this will be implemented. Are they taking overhead shots of Fukushima to see where there is still leakage? I am not a radiation expert, but I don't understand how this would be more effective than a geiger counter. If anybody has any insight I would gladly read a response or any links to some more information.

On one picture you can see how the visual image and the gamma radiation agree at the corner of a wall. You can see that the radiation spot turns 90 degrees with the bottom edge of the wall and how the radioactive materials kind of puddled near the bottom of the wall. It's cool to see that the two images agree.

Also there is video of the actual camera which is pretty big and not so portable. You probably want to keep it in a car most of the time.

The English article edited out some information that was in the Japanese article.

Currently it doesn't tell you the precise amount of radiation being emitted but you get an idea of the highs and lows from it.

The technology that was developed for a detector installed in Japan's next-generation astronomical observatory satellite, the Astro H, to observe gamma ray bursts caused by astronomical events such as old stars exploding into supernovae. JAXA's Professor Tadayuki Takahashi who developed it says, "I want to aim at making this a practical tool quickly." And here is the Prof. Takahashi's cool page [isas.jaxa.jp] and Japanese version [isas.jaxa.jp] which shows news items too.

You will find several English papers on his work by Google: "High-Resolution CdTe Detectors and Application to Gamma-Ray Imaging"

Finally there are links from the Japanese page to a lot of detailed info about the gamma ray camera, though in Japanese there are PDFs including with photos of the supermarket experiment: here [www.jaxa.jp],pdf 1 [www.jaxa.jp]. pdf2 [www.jaxa.jp], here [isas.jaxa.jp].